Plasma Protein-Binding Methods in Drug Discovery

This chapter focuses on the three most widely used in vitro protein binding techniques in pharmaceutical research, which each reflect a diversity of speed, data quality, and complexity. Chromatographic separation using a human serum albumin-immobilized column to allow relative ranking by percent binding is described. Also, 96-well ultrafiltration, perhaps the most widely used in the pharmaceutical industry is discussed. Ultrafiltration allows automation and rapid determinations for multiple compounds in a batch. However, the quality of data from this technique is notoriously dependent on the extent of nonspecific binding of the analyte to the plastic housing or ultrafiltration membrane surface. In addition, 96-well equilibrium dialysis, long considered the definitive or “goldstandard” means of protein binding determinations, is described. Commercial devices have only recently been introduced to allow automation of this technique in a 96-well format.